This invention relates to a MOS field effect transistor circuit exhibiting constant current property irrespective of temperature change.
As large scale integrated circuits (LSI) have been increased in size and popularity, there have been increasing demands for incorporation of an analog-value detecting circuit for detecting a predetermined analog signal level a digital LSI. This analog-value detecting circuit may be used for notifying the user of e.g. wrong operation of the LSI due to fluctuation of a source voltage or heat generation of the LSI exceeding an allowable range. While this type of analog-value detecting circuit may operated as an analog circuit in a digital LSI, the analog circuit composed of circuit elements designed for digital LSI is not generally understood to facilitate analog operation with desired accuracy. Especially in LSI's employing MOS FET's, the operating temperature range is wide, and the current characteristic thereof will be substantially changed according to temperature change within such range. For example, though the circuit constant of an analog circuit may be so set as to enable it to detect current or voltage at a predetermined level, the analog circuit will detect a current or voltage at a level varied with temperature change. Thus, it has conventionally been deemed to be difficult to contruct by using MOS FET's a compact analog-value detecting circuit capable of detecting current or voltage at a predetermined level independently of temperature change within the aforesaid operating temperature range and to incorporate a detecting circuit of large size into a chip of LSI.